Instrument and method for restoring motion to a polyaxial screw

ABSTRACT

A polyaxial screw head remobilizer system for remobilizing a screw body member relative to a head of a polyaxial bone screw includes a barrel body, a handle assembly, an inner shaft, a slide assembly, and a lever. The barrel body includes proximal and distal ends. The distal end includes a plurality of prongs for releasably engaging a plurality of yokes of the polyaxial screw body member to center the inner shaft over the head of the screw. The handle assembly couples to the proximal end of the barrel body. The inner shaft, disposed within the barrel body, includes proximal and distal ends. An engagement feature of the inner shaft mates with pockets of a bushing of the screw body member. The slide assembly is operably coupled to the barrel body and effect translations of the inner shaft. The lever extends from the slide assembly and rotates to actuate the slide assembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/056,573 filed on Oct. 17, 2013, which claims priority fromU.S. Provisional Application Ser. No. 61/716,413 filed on Oct. 19, 2012and entitled “Instrument and Method for Restoring Motion to a PolyaxialScrew” which is incorporated by reference in its entirety herein.

FIELD

The present invention relates generally to an apparatus for internalfixation of the spine and, more specifically, to a remobilizer forrestoring polyaxial motion to a polyaxial screw head that has beenlocked.

BACKGROUND

Certain spinal conditions, including a fracture of a vertebra and aherniated disc, indicate treatment by spinal immobilization. Severalmethods of spinal immobilization are known, including surgical fusionand the attachment of pins and bone plates to the affected vertebras.

Spinal immobilization systems typically require the threaded securementof some form of bone anchor or bone screw-assembly into two or morevertebrae, which entails the drawing of the rod to theanchors/screw-assemblies, or drawing the anchors/screw-assemblies to therod. Spinal screw-assemblies are used to secure a stabilization rod andcomprise various components including a pedicle screw and a body member.The design of the spinal screw-assemblies allows for variable angularmovement of the body member with respect to the pedicle screw with athreaded shaft portion of the screw extending through an opening in anend of the body member.

The next generation of pedicle screws is polyaxial screws, with a bodymember which pivots and rotates about the spherical head of a bonescrew. The bone screw is captured in the body member with a bushing; thebushing in turn accepts a rod after the screw has been placed in thepedicle, and the rod is captured in the bushing/body member assembly byinserting a set screw into the threads of the body member. As with mostpolyaxial pedicle screws, tightening of the set screw applies pressureonto the rod, which translates pressure onto the bushing, which thenapplies pressure on the spherical head of the bone screw, locking thepolyaxial motion. Unlike other polyaxial pedicle screws, the new pediclescrew achieves additional locking because of the design of the screwbushing; the lower portion of the bushing acts like a wedge so whenforce is applied, the bottom of the bushing wedges between the sphericalhead of the bone screw and the body member, providing additional lockingforce.

While this feature provides optimum performance with regards to strengthof the construct in maintaining correction, it can make screw removaldifficult, since the polyaxial motion remains locked due to the wedgingeffect, even after the set screw is removed. In order to restorepolyaxial motion, the bushing must be un-wedged from between the bonescrew head and the body member. The wedge can be knocked loose bytapping the body member of the bone screw with enough force to break thefriction lock of the wedge, but this method may not be consideredfeasible in the case of patients with very poor bone.

As a result, a tool is needed which can interact with the bushing andpull up on it, restoring the bushing to its position prior to lockingand thereby removing the wedge and restoring polyaxial motion.

Previously there has been no reliable method for restoring polyaxialmotion to the screw. There has been no feature on the pedicle screw orbushing which allowed a tool to apply an upward force and remove thewedge. Tools have been attempted which rotate the bushing to “break” thewedge force, but these caused damage to the bushings and could notreliably effect the unlocking. The method of tapping on the screw bodymember to “break” the wedge has already been identified as one whichcannot be recommended for patients with poor bone quality.

SUMMARY OF THE INVENTION

Provided herein are apparatuses, systems, and methods of use for apolyaxial screw head remobilizer.

The polyaxial screw head remobilizer system for remobilizing a screwbody member relative to a head of a polyaxial bone screw generallycomprises a polyaxial screw assembly, a barrel body, a handle assembly,an inner shaft, a slide assembly, and a lever.

The barrel body has a proximal end and a distal end. In someembodiments, the distal end of the barrel body includes engagementfeatures configured to engage with a plurality of yokes of a polyaxialscrew body member and a polyaxial screw, so as to center the polyaxialscrew head remobilizer on the head of the screw. The engagement featuresmay comprise rounded rectangular prongs positioned on the distal end,such that the prongs may be seated in yokes of the screw body member.The barrel body may be made from any suitable material as known in theart including, by way of example and not limitation, stainless steel, athermoplastic or other materials. The barrel body is generallycylindrical in shape; however, it may assume alternative shapes such assquare, rectangular, polygonal, and the like.

The handle assembly is coupled to the proximal end of the barrel bodyfor holding of the polyaxial screw head remobilizer by an operator. Thehandle assembly may be coupled to the barrel body by any suitable methodof attachment such as, for example, a fastener, an aperture, a nut orbolt connection, or the like. In some embodiments, the handle assemblyfurther comprises a mount arm, fixedly coupled to the handle assemblyand the barrel body, the mount arm configured to retain the slideassembly. In some embodiments, the mount arm has an aperture adapted toreceive the inner shaft. In some embodiments, the mount arm isconfigured to slidably couple with the slide assembly, such as, withoutlimitation, by a rail or track. In some embodiments, the mount armfurther comprises a pin or other structure configured to limit thedegree of distal translation of the inner shaft.

The inner shaft is disposed within the barrel body. The distal end ofthe inner shaft further comprises an engagement feature. The engagementfeature is configured to permit positioning of the barrel body and innershaft within the polyaxial screw body member, engagement of theengagement feature with a polyaxial screw bushing, application of aforce to unlock the screw bushing, disengagement of the inner shaft fromthe polyaxial screw bushing, and removal of the remobilizer from thepolyaxial screw body member. In one embodiment, the engagement featureis a plurality of extensions configured to couple with a plurality ofpockets of the polyaxial screw bushing. In some embodiments, the innershaft further comprises a helical trough disposed near the proximal endof the inner shaft.

The inner shaft is generally rounded-rectangular in cross-section.However, the inner shaft may assume alternative shapes, such ascircular, square, cylindrical, polygonal, and the like, having anengagement feature that is adapted for entry into the screw body memberand to frictionally lock with the pockets of the bushing. Alternatively,the inner shaft may be any shape which may be customized for theparticular barrel body utilized. The inner shaft may be made from anysuitable material as known in the art including, by way of example andnot limitation, stainless steel, a thermoplastic or other materials. Inmany embodiments, the inner shaft is fixedly coupled to a stop element.

The slide assembly is slidably coupled to the handle assembly (and/orthe mating arm) and the inner shaft. In some embodiments, the mount armand slide assembly may have apertures configured to permit a portion ofthe inner shaft to be disposed therethrough. In many embodiments, theproximal end of the inner shaft is fixedly coupled to a stop element,the stop element positioned proximal the slide assembly. The stopelement is configured to impede translation of the slide assemblyproximally along the inner shaft. In some embodiments, the slideassembly further comprises a pin configured to interact with the helicaltrough of the inner shaft. In use, the interaction of the pin with thehelical trough causes rotation of the inner shaft as the pin travels thelength of the trough.

The lever rotatably associates with the slide assembly. The lever mayextend from the slide assembly via mechanical attachment by any suitablemethod of attachment, for example, a fastener, an aperture, a nut-boltconnection, a washer, or the like. The lever is further pivotallycoupled to the handle assembly by a suitable mechanical attachment, suchas a pin or the like. The inner shaft may be slidably disposed withinthe barrel body and configured such that the inner shaft may belongitudinally displaced within the barrel body by actuation of thelever and the slide assembly.

In a further embodiment, a spring member is operably coupled to thelever and the handle assembly, such that the spring member urges thelever from an actuated position back to its original position subsequentto actuation of the lever in either the proximal or distal direction.

In use, when the lever is actuated, the lever causes the slide assemblyto slide proximally along the inner shaft. As the slide assemblytranslates, the rotation pin coupled to the slide assembly engages withthe helical trough on the inner shaft, causing the inner shaft to rotateas the pin travels the length of the trough. The rotation of the innershaft causes the engagement feature to couple with pockets of the screwbushing. Once the pin has travelled the full length of the helicaltrough, the slide assembly reaches the stop element, configured toimpede translation of the slide assembly along the inner shaft. Once theslide assembly reaches the stop, continued proximal translation of theslide assembly also translates the stop proximally. Because the stop isfixedly coupled to the proximal end of the inner shaft, the inner shaftis also translated proximally. Because the engagement feature of theinner shaft is coupled with the pockets of the screw bushing, thebushing is pulled proximally, thereby releasing its fixation on the headof the screw. Thus, the polyaxial screw assembly is remobilized.

A polyaxial pedicle screw assembly comprises a screw body member, ascrew bushing, and a polyaxial pedicle screw. The screw body member isgenerally cylindrical in configuration and adapted to receive a headportion of the pedicle screw. The bushing is adapted to fit within thescrew body member between the screw body member and the head portion,and prevent polyaxial motion of the screw when the bushing is locked orpressed into position. The bushing further comprises pockets configuredto engage with the inner shaft of the remobilizer.

The bushing of the polyaxial screw was designed with undercut pockets togive the remobilizer tool a means of attachment. The remobilizer has anouter tube which can be inserted into the yokes of the screw body memberto center the tool on the head of the screw. Inside the outer tube is ashaft which has extensions on the tip which, when rotated, can beinserted in the pockets of the bushing. The tip is actuated by squeezingthe handle; squeezing the handle first pulls a pin in the inner shaft upa helical trough, causing the tip to rotate 90 degrees and inserting theextensions into the mating bushing pockets. Once the pin has traveledthe full distance of the helical trough, it hits a stop, such thatcontinuing to squeeze the handle then pulls the tip of the shaft towardsthe handles. Since the shaft is now mated with the bushing, this pullsthe bushing upwards as well, removing the wedge from the bone screw andbody member and restoring polyaxial motion. Releasing the handlerestores the tip to its original position so it can be removed from thescrew.

A method of using the polyaxial screw head remobilizer tool comprisesthe steps of: inserting an outer tube of the remobilizer into yokes of ascrew body member to center the tool and an inner shaft disposed withinthe outer tube on a head of the screw, in proximity to a bushing memberof the screw body; actuating the tool to rotate the inner shaft suchthat an engagement feature on the tip of the inner shaft mates with aplurality of pockets in the bushing member of the screw; continuingactuation of the tool such that a force is applied to the bushing memberto release a fixation hold between the bushing, the screw head, and thescrew body member, thereby remobilizing the screw head; releasing theactuation of the tool such that the inner shaft derotates and theengagement feature at the tip of the inner shaft disengages from thepockets in the bushing member of the screw; and removing the remobilizertool from the screw body member.

The apparatuses, systems, and methods of use are set forth in part inthe description which follows, and part will be obvious from thedescription or can be learned by practice of the methods, apparatuses,and systems. The advantages of the methods, apparatuses, and systemswill be realized and attained by means of the elements and combinationsparticularly pointed out in the appended claims. It is to be understoodthat both the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the methods, apparatuses, and systems, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying figures, like elements are identified by likereference numerals among the several preferred embodiments of thepresent invention.

FIG. 1 is an illustration of one embodiment of the polyaxial screw headremobilizer.

FIG. 2 is a close up view of the distal end of the remobilizer of FIG.1.

FIG. 3A is an isometric view of a polyaxial screw for use with theremobilizer.

FIG. 3B is a cutaway view of a polyaxial screw for use with theremobilizer.

FIG. 4A is a side view of the distal end of the inner shaft.

FIG. 4B is a side view of the distal end of the inner shaft taken fromview IVB in FIG. 4A.

FIG. 5 is a close up view of the distal end of the tube of theremobilizer, coupled to a polyaxial screw.

FIG. 6 is a side view of one embodiment of the polyaxial screw headremobilizer.

FIG. 7 is a perspective view of one embodiment of the barrel body andthe inner shaft, the inner shaft having an engagement feature at adistal end and a helical trough near a proximate end.

FIG. 8 is an exploded view of the barrel body, inner shaft, mount arm,slide assembly, and stop element.

FIG. 9 is a cutaway view of a remobilizer tip inserted in a polyaxialscrew, upon initial insertion.

FIG. 10 is a cutaway view of a remobilizer tip inserted in a polyaxialscrew after rotation of the remobilizer tip into bushing pockets of thescrew.

FIG. 11 is an exploded view of one embodiment of the polyaxial screwhead remobilizer.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing and other features and advantages of the invention areapparent from the following detailed description of exemplaryembodiments, read in conjunction with the accompanying drawings. Thedetailed description and drawings are merely illustrative of theinvention rather than limiting, the scope of the invention being definedby the appended claims and equivalents thereof.

The words proximal and distal are applied to denote specific ends ofcomponents of the current invention described herein. A proximal endrefers to the end of a component nearer to a medical professional whenoperating the component. A distal end refers to the end of the componentfurther from the medical professional when operating the component.

As shown in FIGS. 1, 6, and 11, a polyaxial screw head remobilizersystem 500 includes a polyaxial screw head remobilizer 100 generallycomprises a barrel body 102, a handle assembly 101 operably coupled to aslide assembly 106, an inner shaft 124 coaxially disposed within thebarrel body, and a lever 112 operably coupled to the slide assembly.Generally speaking, the screw head remobilizer 100 interacts with abushing of a polyaxial screw assembly and longitudinally displaces thebushing to restore the bushing to an unlocked position, thereby removingthe bushing wedge, and restoring polyaxial motion of a screw.

The barrel body 102 has a generally longitudinal axis, wherein thebarrel body 102 includes a proximal end 108 and a distal end 110generally along the longitudinal axis. As shown in FIGS. 1-2 and 5-11,the distal end 110 of the barrel body 102 includes engagement features111 configured to engage with a plurality of yokes (or U-shapedchannels) 223 of a polyaxial screw body member 222 and a polyaxial screw230, so as to center the polyaxial screw head remobilizer 100 on thehead of the screw 230. The engagement features 111 may comprise roundedrectangular prongs positioned on the distal end 110, such that theprongs 111 may be seated in the yokes 223 of the screw body member 222.In alternative embodiments, the engagement features 111 may comprise anyshape suitable for seating in the yokes 223 of the screw body member222, such as, without limitation, rectangular, square, triangular,ovoid, polygonal, and/or the like. Preferably, the engagement features111 are shaped such that, when engaged, the yokes 223 are not permittedto rotate about an axis. The barrel body 102 may be made from anysuitable material as known in the art including, by way of example andnot limitation, stainless steel, a thermoplastic or other materials. Thebarrel body 102 is generally cylindrical in shape; however, it mayassume alternative shapes such as square, rectangular, polygonal, andthe like.

The handle assembly 101 is coupled to the proximal end 108 of the barrelbody 102 for holding of the polyaxial screw head remobilizer 100 by anoperator. The handle assembly 101 may be coupled to the barrel body 102by any suitable method of attachment such as, for example, a fastener, arivet, an aperture, a nut or bolt connection, or the like. In someembodiments, the handle assembly 101 further comprises a mount arm 105,fixedly coupled to the handle assembly 101 and the barrel body 102, themount arm 105 configured to retain the slide assembly 106. In someembodiments, the mount arm 105 has an aperture adapted to receive theinner shaft 124. In some embodiments, the mount arm 105 is configured toslidably couple with the slide assembly 106, such as, withoutlimitation, by a rail or track. In some embodiments, the mount arm 105further comprises a pin or other structure configured to limit thedegree of distal translation of the inner shaft 124.

The inner shaft 124 is coaxially disposed within the barrel body 102 andlongitudinally displaced therein. The distal end of the inner shaft 124further comprises an engagement feature 125. As shown in FIGS. 9 and 10,the engagement feature 125 is configured to permit positioning of thebarrel body 102 and inner shaft 124 within the polyaxial screw bodymember 222, engagement of the engagement feature 125 with a polyaxialscrew bushing 228, application of a force to unlock the screw bushing228, disengagement of the inner shaft 124 from the polyaxial screwbushing 228, and removal of the remobilizer 100 from the polyaxial screwbody member 222.

In one embodiment, as shown in FIGS. 4A and 4B, the engagement feature125 includes a plurality of extensions 126 configured with a steppeddown portion 128 on the distal end of the inner shaft 124. The steppeddown portion 128 allows the engagement feature 125 to coaxially passthrough the plurality of yokes 223, whereby the stepped down portion 128includes a Width W_(S) that is less than a Length L_(E) of theengagement feature 125 and the inner shaft. The engagement feature 125includes a width W_(E), whereby the length L_(E) is greater than theWidth W_(E), as shown in FIGS. 4A and 4B. Preferably, the Width W_(E) isless than the Width W_(Y) of the yokes 223, such that the engagementfeature 125 may longitudinally pass through the Width W_(Y) of the yokes223, as shown in FIG. 3B. Preferably, the Length L_(E) is greater thanthe Width W_(Y) of the yokes 223, such as to engage with a plurality ofpockets 229 of the polyaxial screw bushing 228 (as shown in FIGS. 3A-3Band 9-10) when the inner shaft 124 is rotated after the extensions 126pass through the yokes 223.

Preferably, a quarter-turn rotation of the inner shaft 124 engages theextensions 126 with the plurality of pockets 229. In one embodiment, theplurality of pockets 229 include a Width W_(P) that is greater than theWidth W_(Y) of the yokes 223, and preferably, the Width W_(P) is aboutthe length L_(E) of the engagement feature 125, as shown in FIG. 3B,such as to allow fixedly engagement of the engagement feature 125 andthe plurality of pockets 229. As such, the engagement feature 125 isable to unlock the bushing 228 that wedges the screw head 234 by lockingwith the plurality of pockets 229 and longitudinally moving the bushingproximally away from the screw head 234 and restoring polyaxial motionof the screw 230. In alternative embodiments, the engagement feature 125may comprise generally rectangular lips. More generally, the engagementfeature 125 may have any shape suitable for mating with the particularshape of the pockets 229 of the bushing 228. For example, and withoutlimitation, the engagement feature 125 could be rounded, domed, square,triangular, and/or the like.

As shown in FIGS. 7 and 8, in many embodiments, the inner shaft 124further comprises a helical trough 127 disposed near the proximal end ofthe inner shaft 124. FIG. 7 shows the inner shaft 124 disposed withinthe barrel body 102, with the helical trough 127 disposed proximallyfrom the proximate end 108 of the barrel body 102. The inner shaft 124is generally rounded-rectangular in cross-section. However, the innershaft 124 may assume alternative shapes, such as circular, square,cylindrical, polygonal, and the like, having an engagement feature 125that is adapted for entry into the screw body member 222 and tofrictionally lock with the pockets 229 of the bushing 228.Alternatively, the inner shaft 124 may be any shape which may becustomized for the particular barrel body 102 utilized. The inner shaft124 may be made from any suitable material as known in the artincluding, by way of example and not limitation, stainless steel, athermoplastic or other materials. In some embodiments, the proximal endof the inner shaft 124 may be fixedly coupled to a stop element 122. Theinner shaft 124 may be fixedly coupled to the stop element 122 by anysuitable method of attachment such as, for example, a threaded element,a fastener, a rivet, an aperture, a nut or bolt connection, or the like.

FIG. 8 shows an exploded view of the barrel body 102, inner shaft 124,slide assembly 106, stop element 122, and mating arm 105. The slideassembly 106 is slidably coupled to the handle assembly 101 (and/or themating arm 105) and the inner shaft 124. In some embodiments, the mountarm 105 and slide assembly 106 may have apertures configured to permit aportion of the inner shaft 124 to be disposed therethrough. In manyembodiments, the proximal end of the inner shaft 124 is fixedly coupledto the stop element 122, the stop element 122 positioned proximal theslide assembly 106. The stop element 122 is configured to impedetranslation of the slide assembly 106 proximally along the inner shaft124. In some embodiments, the slide assembly 106 further comprises a pin107 configured to interact with the helical trough 127 of the innershaft 124, as the slide assembly 106 translates along the length of theinner shaft 124. In use, the interaction of the pin 107 with the helicaltrough 127 causes rotation of the inner shaft 124 as the pin 107 travelsthe length of the trough 127. In some embodiments, the helical trough127 is configured to cause a 90 degree rotation of the inner shaft 124as the remobilizer 100 is actuated. In some embodiments, the degree ofrotation is any rotation sufficient to permit the engagement feature 125to couple with the pockets 229 of the bushing 228.

The lever 112 rotatably associates with the slide assembly 106. Thelever 112 may extend from the slide assembly 106 via mechanicalattachment by any suitable method, including, for example, a fastener,an aperture, a nut-bolt connection, a washer, or the like. The lever 112is further pivotally coupled to the handle assembly 101 by a suitablemechanical attachment, such as a pin or the like. The inner shaft 124may be slidably disposed within the barrel body 102 and configured suchthat the inner shaft 124 may be longitudinally displaced within thebarrel body 102 by actuation of the lever 112 and the slide assembly106.

The lever 112 may assume any polygonal shape having a distal end thatcan be longitudinally displaced. The slide assembly 106 and the lever112 may be made from any suitable material as known in the artincluding, by way of example and not limitation, stainless steel, athermoplastic or other materials. In some embodiments, the lever 112 andthe slide assembly 106 may be associated with a locking and/or movingmechanism 133 at the proximal end 108, for incrementally locking and/orproximally moving the inner shaft 124 towards the proximal end 108 andsubsequently releasing the inner shaft 124 to be moved towards thedistal end 110 of the barrel body 102. Alternative spring locked orspring hinged mechanisms may be coupled to the slide assembly 106 andthe lever 112 to move the inner shaft 124 proximally and distally withinthe barrel body 102.

In one embodiment, the locking moving mechanism is a spring member 133a. The spring member 133 a is operably coupled to the lever 112 and thehandle assembly 101, such that the spring member 133 a urges the lever112 from an actuated position back to its original position subsequentto actuation of the lever 112 in either the proximal or distaldirection.

In use, when the lever 112 is actuated, the lever 112 causes the slideassembly 106 to slide proximally along the inner shaft 124 and themounting arm 105. As the slide assembly 106 translates, the pin 107coupled to the slide assembly 106 engages with the helical trough 127 onthe inner shaft 124, causing the inner shaft 124 to rotate as the pin107 travels the length of the trough 127. The rotation of the innershaft 124 causes the engagement feature 125 to couple with pockets 229of the screw bushing 228. Once the pin 107 has travelled the full lengthof the helical trough 127, the slide assembly 106 reaches the stopelement 122, configured to impede translation of the slide assembly 106along the inner shaft 124. Once the slide assembly 106 reaches the stop122, continued proximal translation of the slide assembly 106 alsotranslates the stop 122 proximally. Because the stop 122 is fixedlycoupled to the proximal end of the inner shaft 124, the inner shaft 124is also translated proximally. Because the engagement feature 125 of theinner shaft is coupled with the pockets 229 of the screw bushing 228,the bushing 228 is pulled proximally, thereby releasing its fixation onthe head of the screw 230. Thus, the polyaxial screw assembly isremobilized.

As shown in FIGS. 3A and 3B, a polyaxial pedicle screw assembly 240comprises a screw body member 222, a screw bushing 228, and a polyaxialpedicle screw 230. Polyaxial pedicle screws are more fully disclosed inU.S. publication 2010/0318136, “Polyaxial bone screw assembly,” and inU.S. publication 2008/0243189, “Variable Angle Spinal Screw Assembly”both of which are hereby incorporated by reference in their entirety.The screw body member 222 is generally cylindrical in configuration andadapted to receive a head portion 234 of the pedicle screw 230. Thescrew body member 222 further comprises a plurality of yokes 223,adapted to receive engagement features 111 of the distal end 110 of thebarrel body 102. Generally, the screw body member 222 has a generallytulip shape to form U-shaped yokes 223; however, the screw body member222 may have alternative shapes to form the yokes 223. In alternativeembodiments, the screw body member 222 may have other shapes, such asrectangular, square, diamond, and/or the like. The bushing 228 isadapted to fit within the screw body member 222 between the screw bodymember 222 and the head portion 234, and prevent polyaxial motion of thescrew 230 when the bushing 228 is locked or pressed into position. Thebushing 228 further comprises pockets 229 configured to mate with anengagement feature 125 at the distal end of the inner shaft 124 of theremobilizer 100. The pockets 229 generally have a rectangular lippedshape; however, in alternative embodiments, the pockets 229 may have anyshape suitable for mating with the engagement feature 125 of the innershaft 124, such as square, round, domed, circular, rectangular,triangular, slot, and/or the like.

FIG. 9 shows the prongs 111 of the barrel body 102 and the engagementfeature 125 of the inner shaft 124 coupled with the screw body member222, prior to the lever 112 being actuated. The engagement feature 125is aligned with the prongs 111, so that the barrel body 102 and innershaft 124 may be inserted into the screw body member 222.

FIG. 10 shows the engagement of the engagement feature 125 with thebushing pockets 229 as the lever 112 is actuated and the slide assembly106 initially reaches the stop element 122. The inner shaft 124 has beenrotated 90 degrees to couple the engagement feature 125 with the bushingpockets 229. In some embodiments, the degree of rotation is any rotationsufficient to permit the engagement feature 125 to couple with thepockets 229 of the bushing 228. At this stage, if actuation of the lever112 is continued, the engagement feature 125 will exert an upward forceon the bushing 228, thereby releasing the bushing 228 from fixation withthe screw head 234, remobilizing the polyaxial screw assembly 240.

In some embodiments, the degree of rotation is any rotation sufficientto permit the engagement feature 125 to couple with the pockets 229 ofthe bushing 228.

FIG. 11 shows an exploded view of the polyaxial screw head remobilizer100 with like reference numerals mentioned previously.

A method of using the polyaxial screw head remobilizer tool comprisesthe steps of: inserting an outer tube of the remobilizer into yokes of ascrew tulip to center the tool and an inner shaft disposed within theouter tube on a head of the screw, in proximity to a bushing member ofthe screw body; actuating the tool to rotate the inner shaft such thatan engagement feature on the tip of the inner shaft mates with aplurality of pockets in the bushing member of the screw; continuingactuation of the tool such that a force is applied to the bushing memberto release a fixation hold between the bushing, the screw head, and thescrew tulip, thereby remobilizing the screw head; releasing theactuation of the tool such that the inner shaft derotates and theengagement feature at the tip of the inner shaft disengages from thepockets in the bushing member of the screw; and removing the remobilizertool from the screw tulip.

While the invention has been described in connection with variousembodiments, it will be understood that the invention is capable offurther modifications. This application is intended to cover anyvariations, uses or adaptations of the invention following, in general,the principles of the invention, and including such departures from thepresent disclosure as within the known and customary practice within theart to which the invention pertains.

What is claimed is:
 1. A polyaxial screw head remobilizer system,comprising: a polyaxial screw assembly including a polyaxial screw bodymember, a polyaxial screw member, and a polyaxial bushing member; and aremobilizer tool, the remobilizer tool comprising: a barrel body havinga proximal end and a distal end; a handle assembly coupled to theproximal end of the barrel body; an inner shaft having a proximal endand a distal end, the inner shaft disposed within the barrel body,wherein the distal end of the inner shaft further comprises anengagement feature configured to mate with at least one pocket of abushing of the screw body member; a slide assembly operably coupled tothe barrel body, the slide assembly configured to effect translation ofthe inner shaft; and a lever extending from the slide assembly, thelever being rotatable to actuate the slide assembly.
 2. The system ofclaim 1, wherein actuation of the slide assembly rotates the engagementfeature of the inner shaft to engage the engagement features of theinner shaft are a plurality of prongs, and wherein the polyaxial screwbody member includes a yoke, the plurality of prongs configured toreleasably engage the yoke.
 3. The system of claim 2, wherein theengagement feature further comprise a plurality of extensions configuredwith a stepped down portion on the distal end of the inner shaft, andwherein the polyaxial screw body member includes a yoke, wherein thestepped down portion allows the engagement feature to coaxially passthrough the yoke.
 4. The system of claim 3, wherein the engagementfeature includes a length L_(E) and a width W_(E), whereby the lengthL_(E) is greater than the Width W_(E) and the Width W_(E) is less than aWidth W_(Y) of the yoke, such that the engagement feature maylongitudinally pass through the Width W_(Y) of the yoke.
 5. The systemof claim 4, wherein the Length L_(E) is greater than the Width W_(Y) ofthe yokes, such that the Length L_(E) of the engagement feature engageswith at least one pocket of the bushing of the screw body member.
 6. Thesystem of claim 5, wherein the at least one pocket includes a WidthW_(P) that is greater than the Width W_(Y) of the yokes, and the WidthW_(P) is about the length L_(E) of the engagement feature, to allow theengagement feature to unlock the bushing from the head of the screw. 7.The system of claim 6, wherein the handle assembly further comprises amount arm fixedly coupled to the handle assembly, the mount armconfigured to retain the slide assembly and the mount arm furthercomprises an aperture adapted to receive the inner shaft.
 8. The systemof claim 7, wherein the mount arm is configured to slidably couple withthe slide assembly.
 9. The system of claim 8, wherein the mount armfurther comprises a pin or other structure configured to limit thedegree of distal translation of the inner shaft.
 10. The system of claim1, further comprising a spring member operably coupled to the lever andthe handle assembly, such that the spring member urges the lever from anactuated position back to its original position subsequent to actuationof the lever in either the proximal or distal direction.
 11. The systemof claim 1, wherein the bushing is disposed between the screw bodymember and the head of the screw.
 12. The system of claim 11, whereinactuation of the slide assembly rotates the engagement feature of theinner shaft to engage the at least one pocket of the bushing andlongitudinally displaces the inner shaft towards the proximal end toproximally translate the bushing disposed between the screw body memberand the head of the polyaxial bone screw, remobilizing the polyaxialscrew head.
 13. The system of claim 1, wherein the inner shaft furthercomprises a helical trough configured to interact with a pin coupled tothe slide assembly so as to rotate the inner shaft as the slide assemblytranslates along the inner shaft.
 14. The system of claim 13, furthercomprising a stop member fixedly coupled to the proximal end of theinner shaft, wherein the stop member is configured to impede proximaltranslation of the slide assembly along the inner shaft such thatcontinued proximal translation of the slide assembly also translates theinner shaft proximally.
 15. The system of claim 14, wherein the leverfurther comprises a polygonal shape having a distal end that can belongitudinally displaced.
 16. The system of claim 1, further comprisinga locking or moving mechanism associated with the lever and the slideassembly and located at the proximal end of the barrel body, forincrementally locking or proximally moving the inner shaft towards theproximal end of the barrel body and subsequently releasing the innershaft to be moved towards the distal end of the barrel body.
 17. Thesystem of claim 1, further comprising a spring locked or spring hingedmechanism coupled to the slide assembly and the lever, to move the innershaft proximally and distally within the barrel body.